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AJP - Renal Physiology, Vol 263, Issue 2 243-F250, Copyright © 1992 by American Physiological Society
ARTICLES |
P. Dietl and B. A. Stanton
Department of Physiology, Dartmouth Medical School, Hanover, New Hampshire 03756.
Previously, we found that isoproterenol activates whole cell Cl- conductance by a pathway involving adenosine 3',5'-cyclic monophosphate and protein kinase A (PKA) in a renal cell line (RCCT-28A) derived from the cortical collecting duct. The goal of the present study was to determine whether PKA activates Cl- channels in the apical and/or basolateral membrane. Using the patch clamp technique we found a 305-pS Cl- channel, described previously (22), located exclusively in the apical membrane and an outwardly rectifying Cl- channel (13/96 pS) located exclusively in the basolateral membrane. The outward rectifier was highly selective to Cl- versus cations, was inhibited by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid and 5-nitro-2-(3-phenylpropylamino)-benzoic acid, but was not regulated by cytoplasmic pH or Ca2+. Neither isoproterenol nor PKA activated the 305-pS Cl- channel. In contrast, PKA activated a subset of outwardly rectifying channels in inside-out patches. In another subset of outwardly rectifying channels, formation of the inside-out configuration increased channel activity. These channels, however, were not sensitive to PKA. In conclusion, these experiments show that isoproterenol increases the Cl- conductance of RCCT-28A cells by activating a subset of outwardly rectifying Cl- channels located in the basolateral membrane.
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